A portable computer, such as a notebook, typically includes a variety of parts, such as motherboard, processor, hard disk, keyboard, power supply and display screen. The motherboard, processor, hard disk, power supply and the keyboard are usually housed in a main body. The display screen is housed in a display unit which is separate form the main body. The display unit is connected to the main body by a hinge which allows the display unit to be folded onto the main body, that is, in a fore and aft direction.
In some notebook models, such as a tablet PC, the display unit is connected to the main body by a swivel hinge so that the display unit can be rotated horizontally with respect to the main body. Thus, the display unit can be both folded in the fore and aft direction, and rotated horizontally. In this way, a user of the notebook may rotate the display unit to show the display screen to other people, or even fold the display unit onto the main body with the display screen facing outwards and away from the main body for presentation purposes.
In such a notebook with rotatable screen, cables run through the hinge from the main body to the display unit to supply power and to transmit data to the display screen. Due to the cables passing through the hinge, the hinge is constructed in a manner where the angle of rotation is restricted. In other words, the display unit cannot be rotated indefinitely in any given direction. Also, when the display unit is rotated in one direction, it has to be rotated back to its original position in the opposite direction. For example, if the display unit is rotated in the clockwise direction, it has to be rotated back to its original position in the anti-clockwise direction. This is because the cables through the hinge cannot be infinitely twisted. Furthermore, the frequent twisting of the cables when the display unit is being rotated may cause the cables to wear out or break. In addition, the cables through the hinge also occupy a significant amount of physical space. Therefore, the minimal size of the hinge is also restricted.